clang-format: Fix whitespaces in include directives.

Before (clang-format wouldn't change):
  #include  "a.h"
  #include<a>

After:
  #include "a.h"
  #include <a>

This fixes llvm.org/PR16151.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193683 91177308-0d34-0410-b5e6-96231b3b80d8